Model Output Discussion - 28th November - 4th December

[legritter]

there is even a possibillity that the low rapidly deepens earlier and moves across our south , watch out FRANCE , or it might just be an over cooked burnt low GFS style , but as others have pointed out SOMEWHERE WILL GET IT , ONE TO KEEP AN EYE ON . I PERSONALLY THINK THE COMPUTER IS LATCHING ON TO A SIGNIFICANT WEATHER EVENT .,BUT STAY IN TUNE , IT COULD LOSE IT TOMORROW ,AND BRING IT BACK WEDNESDAY ,PERHAPS A LADY WILL RING THE BEEB TOMORROW , IV MET MICHAEL FISH AND HES A GREAT BLOKE ,SO JUST IN CASE ANYONE SAYS IT, NO IM NOT TAKING THE p...regards legritter

[kold weather]

Ensembles are indeed less dramiatic, but they have lower resolution so may not be clocking onto what is essentially a rather favourable pattern for a biggie.

ECM blows the low up just as it exits England, wind gusts probably of 50-60mph in the east.

[IanM]

If the models were to verify (unlikely at this stage) then consistent wind speeds of around 80-100mph could be expected. If you want to know how to interpret charts have a browse here http://forum.netweather.tv/forum/5-the-netweather-guides/ some good info and knowledge to get you up to speed.

[nick sussex]

Looking at GEFS Nick the Op very much a stormy run against the mean.

http://176.31.229.22...ndres&runpara=0

500hpa much colder and pcpn higher.

A glance at the mean chart at T150 shows a less worrying synopsis.

http://www.meteociel...&ech=150&mode=0 --Op

http://www.meteociel...ode=0&runpara=0 - mean

Quite a dramatic run throughout.

Hi Phil

Wouldn't the higher resolution of the operational run be more adept at the development of this shortwave?

Also I managed to find some info regarding storm Klaus in terms of why it developed in such a way:

Klaus underwent explosive development between the Azores and the Iberian Peninsula at an unusually low latitude. This development was supported by an extended and intense polar jet across the North Atlantic Basin, strong upper-air divergence associated with a second jet streak and an extraordinary export of tropical moisture into the genesis region.

That is from the RMS.

Looking at that I don't think that GFS storm could tap into that level of tropical moisture, but really storms aren't my forte.

Anyway lets hope for a big downgrade in that low tomorrow.

[snowlover2009]

Whatever happens guys, its a very active pattern coming up soon and we are going to get some very interesting storm potential. Interesting time for storm lovers and a seasonal feel and possibility of some wintriness particularly across the north and temperatures look essentially cold in my view, taking into account how strong the wind will be and the direction as well. So I am happy with this. You generally feel the cold more in a cold active outlook than you do with a proper cold spell. Just my opinion. Of course siberian air is still what I would like to see and definitely would freeze us, just saying. Its going to feel quite cold in the strong winds. I felt it this morning and it was a slight breeze, could have been just me or the mild autumn.

Edited November 28, 2011 by snowlover2009

[feb1991blizzard]

Hi Phil

Wouldn't the higher resolution of the operational run be more adept at the development of this shortwave?

Also I managed to find some info regarding storm Klaus in terms of why it developed in such a way:

Klaus underwent explosive development between the Azores and the Iberian Peninsula at an unusually low latitude. This development was supported by an extended and intense polar jet across the North Atlantic Basin, strong upper-air divergence associated with a second jet streak and an extraordinary export of tropical moisture into the genesis region.

That is from the RMS.

Looking at that I don't think that GFS storm could tap into that level of tropical moisture, but really storms aren't my forte.

Anyway lets hope for a big downgrade in that low tomorrow.

Mind you Nick the heavier the PPN the more likely to turn wintry in the North so for drifting snow potential the deeper the low the better in that respect but obviously you have bad experience of storms so i appreciate your viewpoint.

Edited November 28, 2011 by feb1991blizzard

[Michael Kaii]

a know this is nothing to do with model output but Billmly what a storm! if this comes ture Would it not cause a storm surge type of storm Esp with the High tide for holland and Belgum?

[Guest Kent-Weather]

One run on the GFS with little support which shows a hurricane force storm a week into the future and people are now say it's going to come off!

Are you sure this is the only GFS run it's been appearing on? Because it's also been on yesterday's 06z/18z.. this mornings 06z, todays 12z to a certain degree although not as dramatic and now reoccurs on the latest 18z run with very very similar positioning and wind gusts, and I've been saving the charts (besides the 12z admittedly). So far it has managed to work its way down from T+192 and is now, based on the 18z sitting there once again at T+150. Whilst I agree that it's gone from FI to medium range.. I'm almost stunned by GFS consistency in its most 'volatile' stages of trustworthy-ness. By no means am I saying such a storm system is certain - it's still got a very long way to go in terms of time but if GFS keeps this up AND it verifies - this will be one of the most astonishing calls by GFS I've ever seen in the 5+ odd years model watching.

Also, it's not just GFS that had the idea of such a system developing around the 4/5th December. The ECM 12z output on the 25th November also had quite a deep low pressure in the North Sea giving Northerly gales down the Eastern side of the UK for the 4th December!! I personally am following this like a hawk

[BlueHedgehog074]

(my opinions on tonights models)

The GFS 18Z shows an unsettled outcome, generally, with periods of rain and showers crossing the land in the next week or so! Some of this will be wintry in the North with the upper temperatures colder their. There will be some briefer settled spells between the bands of preciptation, with Friday looking to be the driest of this week. Friday shouldn't feel that windy either with the isobars not that tightly packed. It will feel a bit chillier everywhere, too, thanks to cooler air spilling South-Eastwards on the North-Eastern part of that High to the West-South-West....

Friday morning's pressure charts and wind speed:

Winds may pick up a little on Friday night as another Low attempts to spill in from the West, with the centre of the Low tracking across the North. And the weather starts becoming windier and unsettled again for the weekend.

Things start becoming less certain as we progess into next week, and I do feel their could be changes to be made regarding the severity and track of that Sunday night 'exploding Low'. Tis true that the GFS does have a habit of over-deepening Lows at times, and we may find that we will end up with a less potent version, or that it ends up tracking further North.

The 12Z ECMWF goes for a fairly similar outlook - though Southern areas would probably become more settled in Deep FI. ECMWF also seems to show a possible cut-off Low for Southern areas bringing the risk of stormy weather and strongs winds through late Sunday to Monday morning. Heavy rain, possibly sleet and hill snow will be accompanied by this system as it attempts to bring down colder air.

[Cheese Rice]

If we look across the models we see the

ECM-

GFS-

JMA-

NOGAPS-

GEM-

Every model goes for a deep area of low pressure, only the GEM ensembles don't. But the general consciousness is a deep low will pass the UK. Interesting as I didn't expect it too be the case due to only seeing it for the first time on the 18Z.

Edited November 29, 2011 by Cheese Rice

[Liam J]

Are you sure this is the only GFS run it's been appearing on? Because it's also been on yesterday's 06z/18z.. this mornings 06z, todays 12z to a certain degree although not as dramatic and now reoccurs on the latest 18z run with very very similar positioning and wind gusts, and I've been saving the charts (besides the 12z admittedly). So far it has managed to work its way down from T+192 and is now, based on the 18z sitting there once again at T+150. Whilst I agree that it's gone from FI to medium range.. I'm almost stunned by GFS consistency in its most 'volatile' stages of trustworthy-ness. By no means am I saying such a storm system is certain - it's still got a very long way to go in terms of time but if GFS keeps this up AND it verifies - this will be one of the most astonishing calls by GFS I've ever seen in the 5+ odd years model watching.

Also, it's not just GFS that had the idea of such a system developing around the 4/5th December. The ECM 12z output on the 25th November also had quite a deep low pressure in the North Sea giving Northerly gales down the Eastern side of the UK for the 4th December!! I personally am following this like a hawk

It's the only run the GFS has progged a storm with hurricane like wind speeds, it has been showing various depressions crossing the UK but this is the first one being blown up to this severity.

In the mean time we could be looking and wind gusts up to and over 70mph tomorrow for a time towards the west from N England southwards, very squally conditions could materialise as the cold front moves through.

Edited November 29, 2011 by Liam J

[feb1991blizzard]

The storm on the GFS 18z not completely without support from ensembles, there are a few members backing the OP, take a look at the lincolnshire MSLP ensembles.

http://www.netweathe...ensviewer;sess=

Edited November 29, 2011 by feb1991blizzard

[jonnybradley]

I know this has already been discussed in this thread but thought it was worth posting the link again, especially after Nick's last post. Sorry to those that have already seen it. It relates to Sat 3rd but seems related to me?

For those interested, the first indication of the low(s) for the weekend can be seen on the T+120 Met O Fax chart, the area with no isobars close by Newfoundland. All the models then treat it rather differently then as it starts to develop, a good intro is to read the post by chio on the dedicated thread to it. Its a result of the very large temperature differences north to south between Greenland and the SE end of the north Atlantic which is causing this run of deep lows tracking across the ocean towards the NW of our shores. As each tracks east so the air is slowly turning a little less mild from the north and this will continue into next week.

I think this is the link to that thread, very interesting thread (even if I did only understand it in parts:)

[Guest Kent-Weather]

It's the only run the GFS has progged a storm with hurricane like wind speeds, it has been showing various depressions crossing the UK but this is the first one being blown up to this severity.

Lol no it isn't. Yesterday's 18z also had very similar wind gusts (not wind speeds, no wind speed has been close to hurricane force - 75mph) for this particular storm

Edited November 29, 2011 by Kent-Weather

[Snowmad79]

Up to and including 120hrs all the models are the same this morning, Snow potential for Scotland N ireland, parts of S Ireland and Northern England (mainly NWern parts) from Saturday noon into saturday night as the colder air around -5 passes over us. Though the initial band of rain clears ahead of the cold front, any ppn that follows through with the cold front should give snow or something wintery to the parts mentioned above, the higher you are the more favourable for snow.

PPN

Shame that heavier band passes before the cold air digs in but still potential is there. At 144hr all 3 models then show some degree of a new LP cell splitting off the LP situated to our immediate NE but forming in different places. UKMO has it west of Ireland kicking in with a bit of a SWerly flow which would deflect those -5 uppers.

The GFS has it bang over me (MOVE DAMN IT!) and would also see the colder uppers shifted north briefly and the ECM has this little feature developing off the east coast keeping the NWerly flow going.

After 144hr the little split off LP then whizzes off into Europe and the NWerly flow is maintained to a degree but along with HP ridging over from the west bringing in milder air and turning any PPN to rain. Looks to remain quite windy too.

What I dont see is on these runs this morning is any tendancy at all for height rises to our east or north east.

[Snowmad79]

Snowmad, being further North and with elevation will help if some of the charts being projected come off, albeit it is a small window of opportunity anyway. Possibly one of those situations where as soon as it is cold enough for snow there is no PPN, and as soon as there is PPN, it's warm enough for rain again.

Also even if the set-up is the most favourable of what is being projected, for areas further South - the Irish Sea is warm in early December (anomalously so right now) and this would make any Cheshire gap or feed of showers into NW England rain or sleet.

Indeed, forgot to mention the futher north and west the better (did say height). And I also class sleet as wintery . 1 day is about the usual from a toppler so hopefully there will be enough ppn left as the cold air digs in to give me something along the lines of snow. I say snow because usually, 1/2 mile down the road may get sleet at best where as I get snow, being on a fairly high point of the pennines.

[Liam J]

Lol no it isn't. Yesterday's 18z also had very similar wind gusts (not wind speeds, no wind speed has been close to hurricane force - 75mph) for this particular storm

Quite a bit of difference tbh - Sundays 18z had a depression of 974hpa with severe gales, Mondays 18z has a depression of 952hpa and would result in violent srorm force 11 to near hurricane force mean speeds with gusts to 100mph over exposed Holland. As I said it was the first time the GFS has blown a

low up to this severity for the event next week!! 00z has downgraded this event anyhow.

GFS has brought back the wind event for N&W UK Wednesday night, I thought this might happen as I mentioned yesterday.

Edited November 29, 2011 by Liam J

[Cecil Hogmanay Melchett]

Indeed, forgot to mention the futher north and west the better (did say height). And I also class sleet as wintery . 1 day is about the usual from a toppler so hopefully there will be enough ppn left as the cold air digs in to give me something along the lines of snow. I say snow because usually, 1/2 mile down the road may get sleet at best where as I get snow, being on a fairly high point of the pennines.

Your very high up at 300m mate if gfs is near the amrk you'll see lying snow at some point in the next 7 days im sure of it.

[Teesdale]

Quite a bit of difference tbh - Sundays 18z had a depression of 974hpa with severe gales, Mondays 18z has a depression of 952hpa and would result in violent srorm force 11 to near hurricane force mean speeds with gusts to 100mph over exposed Holland. As I said it was the first time the GFS has blown a

low up to this severity for the event next week!! 00z has downgraded this event anyhow.

GFS has brought back the wind event for N&W UK Wednesday night, I thought this might happen as I mentioned yesterday.

Some violent storms on some of the 00z run early next week.

http://176.31.229.228/modeles/gens/run/gens-1-1-174.png?0

http://176.31.229.228/modeles/gens/run/gens-6-1-150.png?0

http://176.31.229.228/modeles/gens/run/gens-10-1-150.png?0

http://176.31.229.228/modeles/gens/run/gens-13-1-156.png?0

http://176.31.229.228/modeles/gens/run/gens-14-1-168.png?0

http://176.31.229.228/modeles/gens/run/gens-18-1-156.png?0

[johnholmes]

The 3 main models have quite different charts at T+144, one has a deep trough low over the Humber, one over Blackpool and one has a more open looking feature even further west.

Maybe the best way to follow where it might go is to follow the Met O Fax charts?

[shedhead]

No sig changes in the overnight runs, with wet, windy and even occasional stormy weather being the main features. Also looks like we should see a couple of chilly days, but overall temps look like being pretty close to average, perhaps rising into the mild category again for most later next week if as expected, winds swing back towards the southwest.

Edited November 29, 2011 by shedhead

[Thundery wintry showers]

Mind you Nick the heavier the PPN the more likely to turn wintry in the North so for drifting snow potential the deeper the low the better in that respect but obviously you have bad experience of storms so i appreciate your viewpoint.

The above holds true when all other things are equal, but all other things aren't equal when we're talking about the depth of a depression. When we get a deeper depression, it tends to be associated with a warmer depression core and also with the low tracking a bit further north- thus greater likelihood of a major snowstorm for a select few (mostly on high ground) and rain or sleet for most of the rest of us.

The GFS 18Z run with its mega-low ended up with rather less cold pooling over the UK than this morning's runs.

It still looks "game on" for a spell of cold zonality starting on Saturday and lasting between three and five days, though I remain wary of the models' tendency to overdo these things and won't be surprised if that window shortens to 36-48 hours. Winds are also likely to reach gale force for many areas on Saturday.

Before that, quite a lot of weather activity during the coming week. Today and tomorrow are both set to see rain belts moving in from the west and above-average temperatures, with a secondary low tomorrow cutting off the polar maritime regime, and strong winds, perhaps touching gale force in exposed areas. With a sluggish north-westerly regime for central and northern parts on Thursday and Friday, probably dry and sunny for the majority with just a scattering of showers in the west, with snow on high ground, while southern England looks set to have rain on Thursday.

[Stratocumulus perlucidus]

06z os out and the 522 dam line Is over half the country on monday evening.

http://hw.nwstatic.co.uk/gfsimages/gfs.20111129/06/150/hgt500-1000.png

Edited November 29, 2011 by saintpeter

[AWD]

06z GFS has two LP systems over the weekend! The first one at the beginning of the weekend crosses NNE over Scotland bringing gales and severe gales to the north! Then later Sunday and into Monday there is a smaller, but still quite potent LP over the north sea Belguim area, bringing strong winds to the south, and more especially south east of the UK!

Also on Monday there is a brief, but rather potent pM airflow over the

entire UK, with -5c uppers down to the south coast! These quickly get shunted east on Tuesday though, ahead of the next LP system in what looks to be a very active Atlantic dominated run!

Until FI that is, when HP ridges up from the SSW and settles things down

somewhat! Deep FI and HP brings very mild and settled conditions to the UK! A cold plunge into eastern Europe though!

Edited November 29, 2011 by Active Weather Dude

[rich1]

Reckon that HP in FI would be mild to start with but centered further north for a few days would turn chillier with frost and fog becoming more apparent. Whilst not deep cold its not a terrible or an implausible scenario. A traditional winter anticyclone

seen a few LRF's with that being a feature around the middle-back end of the month, though its one of several scenarios at that range. Next best thing to snow at Christmas would be an intense one of these things plonked over the centre-north of the uk with sunshine and frosty nights. Too far south it becomes extended mediocrity but should it push further north the end result may become more palatable

Looks like a normalish december is a possibility, stormy disturbed weather for 10-14 days followed by a drier period is possible [not definite but possible]. After then, we will see. But its not a decided scenario at that range all the same

Edited November 29, 2011 by rich1